Inspection Procedure 19: Engine-A/T-ECU power supply, engine control relay, ignition switch-IG1 system












OPERATION



  • The battery voltage is applied to the engine control relay (terminal No. 2 and No. 3).
  • The engine-A/T-ECU (terminal No. 57) makes the power transistor in the unit be in "ON" position and makes currents go on the engine control relay coil, and that makes the relay be in "ON" position.
  • When the engine control relay is in "ON" position, the battery voltage is supplied to the engine-A/T-ECU (terminal No. 34 and No. 43), the sensor and the actuator from the engine control relay (terminal No. 1).

FUNCTION



  • When the ignition switch ON signal is input to the engine-A/T-ECU, the engine-A/T-ECU places the engine control relay in the ON position. Accordingly, the battery voltage is supplied to the engine-A/T-ECU, sensor and actuator.

PROBABLE CAUSES



  • Failed engine control relay
  • Open/short circuit in engine control relay circuit or loose connector contact
  • Failed engine-A/T-ECU

DIAGNOSIS PROCEDURE
note
    *1: L.H. drive vehicles
    *2: R.H. drive vehicles

STEP 1. Check battery voltage.

  • Measure battery voltage during cranking.
OK: 8 V or more

Q. Is the check result normal?
Go to Step 2 .
Check battery (Refer to GROUP 54A - Battery - On-vehicle Service - Battery test ).

STEP 2. Connector check: B-15X engine control relay connector

Q. Is the check result normal?
Go to Step 3 .
Repair or replace the connector.

STEP 3. Check engine control relay.

  • Check engine control relay (Refer to ).

Q. Is the check result normal?
Go to Step 4 .
Replace the engine control relay.

STEP 4. Perform voltage measurement at B-15X engine control relay connector.

  • Remove relay, and measure at relay box side.
  • Voltage between terminal No. 2 and earth, also between terminal No. 3 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 5 .

    Check intermediate connector A-03*1 or D-137*2, and repair if necessary. If intermediate connector is normal, check and repair harness between B-15X (terminal No. 2 and terminal No. 3) engine control relay connector and battery.

    • Check power supply line for open/short circuit.

STEP 5. Connector check: D-214 engine-A/T-ECU connector

Q. Is the check result normal?
Go to Step 6 .
Repair or replace the connector.

STEP 6. Perform voltage measurement at D-214 engine-A/T-ECU connector.

  • Measure engine-A/T-ECU terminal voltage.
  • Ignition switch: ON
  • Voltage between terminal No. 34 and earth, also between terminal No. 43 and earth.
OK: System voltage

Q. Is the check result normal?

    Check and repair harness between B-15X (terminal No. 4) engine control relay connector and D-214 (terminal No. 57) engine-A/T-ECU connector.

    • Check signal line for short circuit.
Go to Step 7 .

STEP 7. Check harness between B-15X (terminal No. 1) engine control relay connector and D-214 (terminal No. 34 and No. 43) engine-A/T-ECU connector.
note Before checking harness, check intermediate connector C-111, and repair if necessary.

  • Check power supply line for open/short circuit and damage.

Q. Is the check result normal?
Go to Step 8 .
Repair the damaged harness wire.

STEP 8. Perform voltage measurement at D-214 engine-A/T-ECU connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 50 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 11 .
Go to Step 9 .

STEP 9. Connector check: D-309 ignition switch connector

Q. Is the check result normal?
Go to Step 10 .
Repair or replace the connector.

STEP 10. Check ignition switch.

  • Check ignition switch (Refer to GROUP 54A - Ignition Switch - Inspection ).

Q. Is the check result normal?

    Check intermediate connectors D-231, D-403 and D-405, and repair if necessary. If intermediate connectors are normal, check and repair harness between D-309 (terminal No. 2) ignition switch connector and D-214 (terminal No. 50) engine-A/T-ECU connector.

    • Check output line for open/short circuit and damage.
Replace the ignition switch.

STEP 11. Check harness between B-15X (terminal No. 4) engine control relay connector and D-214 (terminal No. 57) engine-A/T-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 12 .
Repair the damaged harness wire.

STEP 12. Check harness between B-15X (terminal No. 2 and No. 3) engine control relay connector and battery.
note Before checking harness, check intermediate connector A-03*1 or D-137*2, and repair if necessary.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 13 .
Repair the damaged harness wire.

STEP 13. Check harness between D-309 (terminal No. 2) ignition switch connector and D-214 (terminal No. 50) engine-A/T-ECU connector.
note Before checking harness, check intermediate connectors D-231, D-403 and D-405, and repair if necessary.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 14 .
Repair the damaged harness wire.

STEP 14. Connector check: D-14 earth connector.

Q. Is the check result normal?

    Check and repair harness between D-214 engine-A/T-ECU connector and D-14 earth connector.

  1. Check and repair harness between D-214 (terminal No. 33) engine-A/T-ECU connector and D-14 (terminal No. 2) earth connector.
  2. Check and repair harness between D-214 (terminal No. 42) engine-A/T-ECU connector and D-14 (terminal No. 1) earth connector.

  • Check earthing line for open circuit and damage.
Repair or replace the connector.